Practical analysis of 8051 microcontroller (taking STC89C52RC as an example) | 09 - LED dot matrix display of numbers

1 LED dot matrix

LED dot matrix is ​​a display device composed of light-emitting diodes. It can be seen everywhere in our daily electrical appliances and is widely used in bus station announcers, advertising screens, etc. The 8*8 dot matrix is ​​usually used more often, and then multiple 8*8 dot matrices can be used to form LED dot matrix display screens with different resolutions. For example, 16*16 dot matrix can be composed of 4 8*8 dot matrices. Therefore, if you understand the working principle of 8*8LED dot matrix, other resolution LED dot matrix display screens are the same. Here we will introduce 8*8LED dot matrix.

working principle:

The 8*8 dot matrix is ​​composed of 64 light-emitting diodes, and each light-emitting diode is placed at the intersection of the row and column lines. When the corresponding row is set to 1 level (the row is connected to the anode of the diode, so it is a high level) and the column is set to 0 level (the column is connected to the cathode of the diode, so it is a low level), the corresponding diode will light up; if you want to light up the first diode, connect the A1 pin to a high level and the K1 pin to a low level, then the first point will light up; if you want to light up the first row, connect the A1 pin to a high level, and (K1, K2, K3, K4, K5, K6, K7, K8) these pins to a low level, then the first row will light up; if you want to light up the first column, connect the K1 pin to a low level, and (K1, K2, K3, K4, K5, K6, K7, K8) to a high level, then the first column will light up.

Next, we will understand its use in depth by displaying a dot and a number on the LED dot matrix.

2 Schematic diagram

① 8*8 LED dot matrix schematic diagram:

② 74HC595 schematic diagram (connect OE to GND at the JOE pin header):

③ MCU schematic diagram:

3 Procedure

① Light up the first point in the upper left corner:

#include "reg51.h" //This file defines some special function registers of the microcontroller

#include

typedef unsigned int u16;   //declare and define the data type

typedef unsigned char u8;

sbit SRCLK=P3^6; //Storage register clock pin (data input clock line)

sbit RCLK=P3^5; //Shift register clock pin (output memory latch clock line)

sbit SER=P3^4; //Serial data input pin

/***********************************************************************************

* Function name: Hc595SendByte(u8 dat)

* Function : Send one byte of data to 74HC595

* Input : None

* Output          : None

***********************************************************************************/

void Hc595SendByte(u8 dat)

{

u8 i;

SRCLK=0; // Initialize the data input clock line

RCLK=0; // Initialize the output memory latch clock line

for(i=0;i<8;i++)

{

SER=dat>>7; //Send from the highest bit Example: 1111 0000, the highest bit is 1, shift right 7 bits, and finally become 1, so the highest bit is saved

dat<<=1; // Shift left to become the second highest bit, continue with the previous example, shift left to become the second highest bit, shift right 7 bits to become the second highest bit

SRCLK=1; // From 0 to 1, that is, from low level to high level, the shift register rises, and the data is stored in the shift register

_nop_();

_nop_();

SRCLK=0; // Reset pin

}

RCLK=1; // shift register clock pin plus rising edge, data parallel output

_nop_();

_nop_();

RCLK=0; // Reset pin

}

/***********************************************************************************

* Function name: main

* Function : Main function

* Input: None

* Output    : None

***********************************************************************************/

void main()

{

Hc595SendByte(0x80); // Write 0b10000000 to make the D7 pin output high level

P0=0x7f; // Write 0b01111111 to make the P07 pin output low level

while(1);

}

② Display the number 0 on the dot matrix:

#include "reg51.h" //This file defines some special function registers of the microcontroller

#include

typedef unsigned int u16;   //declare and define the data type

typedef unsigned char u8;

sbit SRCLK=P3^6; //Storage register clock pin (data input clock line)

sbit RCLK=P3^5; //Shift register clock pin (output memory latch clock line)

sbit SER=P3^4; //Serial data input pin

// Define the display position of number 0

u8 LedSeg[]={0x00,0x00,0x3e,0x41,0x41,0x41,0x3e,0x00};

u8 LedPos[]={0x7f,0xbf,0xdf,0xef,0xf7,0xfb,0xfd,0xfe};

/***********************************************************************************

* Function name: delay

* Function    : Delay function, when i=1, the delay is about 10us

***********************************************************************************/

void delay(u16 i)

{

while(i--);

}

/***********************************************************************************

* Function name: Hc595SendByte(u8 dat)

* Function : Send one byte of data to 74HC595

* Input : None

* Output          : None

***********************************************************************************/

void Hc595SendByte(u8 dat)

{

u8 i;

SRCLK=0; // Initialize the data input clock line

RCLK=0; // Initialize the output memory latch clock line

for(i=0;i<8;i++)

{

SER=dat>>7; //Send from the highest bit Example: 1111 0000, the highest bit is 1, shift right 7 bits, and finally become 1, so the highest bit is saved

dat<<=1; // Shift left to become the second highest bit, continue with the previous example, shift left to become the second highest bit, shift right 7 bits to become the second highest bit

SRCLK=1; // From 0 to 1, that is, from low level to high level, the shift register rises, and the data is stored in the shift register

_nop_();

_nop_();

SRCLK=0; // Reset pin

}

RCLK=1; // shift register clock pin plus rising edge, data parallel output

_nop_();

_nop_();

RCLK=0; // Reset pin

}

/***********************************************************************************

* Function name: main

* Function : Main function

* Input: None

* Output    : None

***********************************************************************************/

void main()

{

u8 i;

while(1)

{

P0=0x7f; // Initialize port P0

for(i=0;i<8;i++) //8 rows and 8 columns, bit selection is performed while scanning rows, so there are 8 loops in total

{

P0=LedPos[i];   //Send bit selection data to control P0 port

Hc595SendByte(LedSeg[i]); //Send segment selection data to control 74HC595

delay(100);    //delay, the speed cannot be observed by naked eyes

Hc595SendByte(0x00); //Blank to prevent affecting the next scan

}

}

}